Near the Earth's surface, geomagnetic effects are readily detectable
with a simple compass. A natural bar magnet, mounted on a pivot, will
do. The Earth's magnetic field strength near the surface is half a Gauss
( 50 microTesla), and
surface magnetic field lines are pointing towards
and entering the Earth's crust near the North geographic pole - the
entry point in the crust is currently near 70 - 75° longitude
West, and near 79 - 80° latitude North.

Are some animals endowed with a sixth (magnetic) sense ? Migratory sea
turtles can detect changes in the Earth's magnetic field strength at
different places in their trips, as well as changes in the Earth's
magnetic field inclination/direction
(Lohmann & Lohmann,
1996).
The Earth's magnetic field direction can also be detected or sensed by
many types of bees and birds, notably pigeons and garden warblers
(Weindler et al. 1996;
Gould 1996b),
as well as by many types of whales and fish, notably eels, salmons,
yellowfin tunas, sea turtles, and trouts (e.g.,
Gould 1996a;
Kirschvink 1997).

The threshold of magnetic intensity variation necessary to induce
behavioral responses is around 1000 milliGauss for some birds,
honeybees, pigeons, and whales, while
it is 500 milliGauss in rainbow trouts
(Walker et al. 1997).

In rainbow trouts, a study identified an area in the olfactory nose of
the trout
where a form of biogenic magnetite could be found, attached to the ramus
(ros V) of the
trigeminal sensory nerve going to the brain. The apparent proximity of
the magnetic sensor
and the olfactory reception raises the possibility that olfactory
impairment would also
produce magnetic impairment, which is the case in homing pigeons (e.g.,
Walker et al. 1997).

From time to time, energetic jets of particles are emitted by the Sun and
are channeled by the Earth's magnetic field toward the two poles of the
Earth, where they
encounter at high speed the gas particles in the atmosphere. The ensuing
collisions energize the local gas particles; these auroral particles
then de-excite by emitting flashes
of optical light at an altitude of about 100 km. Against solar
particles, the Earth's magnetic field acts as a shield protecting Life,
and as a channel for space particles. The existence of the Earth's
magnetic field is thus revealed when illuminated by the auroral
particles in the atmosphere, producing a show often described as
'dancing curtains'. The dancing is due to the intermittent and varied
arrivals of different amounts of solar particles at different times and
directions.

Figure 1 shows typical transmission lines on
Earth, above the ground.
Solar magnetic storms can have effects on these above-ground
transmission lines, through their magnetic induction. In 1989, the
Canadian province of Québec suffered a massive electricity blackout,
brought on by a space surge, costing Hydro-Québec $10 M Cdn; the
large surge in
electrical activity from space had short-circuited these electric
transmission lines and the overall system on Earth.

Figure 1. Typical example of electrical
transmission lines to transport electricity on Earth.
Magnetic fields are shown following the usual right-handed screw system
(right thumb
towards direction of electric current I). Since the electric currents
are mostly alternating,
the senses of the assoicated magnetic fields will also reverse with
time. The above-ground
lines can be seriously affected by the passage of solar magnetic storms
speeding away from the Sun and encountering the Earth.

In 1994, Canada's Anik-E1 and Anik-E2 communication satellites were hit
by a
magnetic blast from the Sun, disrupting Canadian TV operations for days.
In January 1997, another solar energy burst permanently disabled the US
AT&T satellite, costing nearly $150 millions US (e.g.,
Curren 1997)
- it did this pushing the Earth's magnetosphere boundary
much closer to Earth, inside the satellite's orbit around Earth,
exposing the satellite to the Sun's blasts (e.g.,
Kiernan 1997).